My apologies if it was discussed before, and I simply missed it (I just started reading Camera Labs).

There are places which show examples of hot pixels issue in K20D (various K20D bodies), and describe them it in some details (Google if you are curious). Pentax eventually confirmed the problem and will release a new firmware to address the issue - most likely not by really fixing (I do not believe that it is fixable), but by improving algorithm of dynamically masking the hot pixels with interpolated values.

There are many interesting points here, and one needs to understand that most cameras are also affected by similar problem, but each handles it a bit differently: some reasonably well, other so-so. Good cooling of the sensor is the best solution, but not practical in consumer equipment beyond a small, passive insufficient heatsink. As the sensors become more and more stressed beyond what they can cleanly deliver I observe (sometimes with amusement) what manufacturers do in firmware to compensate. None of the manufacturers documents what they did in firmware beyond a few words, so back engineering or testing the results is the only way to find more about it.

I am just curious why comprehensive K20D Camera Labs test does not mention it at all? Did I miss something, did the tester(s) were unaware of the issue and the fact that Pentax confirmed it? A few other tests I read here are very good, thus such omission almost looks to me like I missed something.

I understand, you were not sufficiently curious to investigate further why others have seen this problem (and posted tests showing it), and why Pentax is working on a fix for something you did not find in your tests.

byte, my understanding is that hot pixels are simply noise manifestation of digital imaging sensor (also named 'dark noise', or 'image noise'). More of them appear when the sensor overheats, thus prolonged use of live view is one scenario which could trigger more of them to appear, very long exposures (night shots) is another. See for example this from Hasselblad:

"Image noise in the Hasselblad H3D-II has been significantly reduced by improving the cooling of the sensor, achieved by attaching to the CCD a physical heatsink, which dissipates the heat generated to the entire camera body and considerably lowers the temperature of the system"

I found it strange that a reputable site can test the same camera, and does not even mention the issue which was already widely known and discussed elsewhere, also acknowledged by Pentax. Not seeing something which many other people saw is significant, and should lead to: "why I am not seeing this?" or "how is my test different?" or "are there different K20D bodies being sold?" etc, etc.

BTW, I do not believe that Pentax fix addressed the issue, but as at this stage I can not re-test myself, I am not in a position to contribute anything more.

byte wrote:

darius, I believe hot pixels rarely show up during normal usage. However they may appear after extensive use of live view as said by reviewers of other website.

I'm sure potential purchasers of the K20D will be interested in the issue you have flagged. There is a good write-up about this in the PDF document Short analysis of K20D hot pixel phenomenon. The conclusions presented in this document are as follows:

There is no significant difference in hot pixels between Pentax *istDS and K20D.

Hot pixels shouldn't be a problem for normal exposure times.

Otherwise, the hot pixels are real and w/o dark frame subtraction, there too many of them. Most of them are dim, though.Dark frame subtraction seems to stop doing its job for exposures of 1000s and longer. Still works for 150s at ISO400, though.

Hot pixels tend to form clusters and such clusters, most likely, escape the RAW converter removal.

So, all in all, these seem to be normal properties for a DSLR CMOS/CCD sensor.

The only finding left as a concern for the K20D is a single, non reproducible image from the K20D with excess hot pixel noise.

By the way, I suspect that a couple of typos have crept into the quoted text but the overall meaning is clear, especially in light of the penultimate paragraph.

In light of this report it is certainly not surprising that Gordon didn't see the problem. Indeed, from the above it might even be suspected that the seriousness of the problem has been over-stated and your own worries about the camera and Gordon's methodology have fallen prey to that process.

Anyway, I forget my manners and as this is my first reply to one of your posts may I wish you my usual warm welcome tot the CameraLabs forums. Are you already a DSLR owner or are you contemplating becoming one? Is (or was) the K20D on your shortlist?

Thank you for your response, and the pointer to the hot pixels PDF doc, this is first informative quality material I have seen which really explains the issue. falconeye should be congratulated.

And thank you for your welcome message, I appreciate that. I am a professional engineer with around 40 years of industrial experience in high precision mechanical and electronics industry. I did own many cameras in my life, at the moment I have access to and I am using various equipment, so I do not have urgent need to buy any, but I will probably get a camera soon anyway. Overall I am very disappointed with current development in this field. By the way, I believe that I am very experienced engineer, but also totally average photographer.

Over the last 40 years or so I observed tremendous progress in my field, but not in the consumer digital photography which in my view created almost nothing conceptually new. All I see are hybrid designs, very similar between different brands, where electronics is simply added to old SLR mechanical design and practically no new ideas are developed. I may as well go to a shop and say: "just give me a dSLR for around $1,000 please, I don't care which brand". And I know that I will get one of very similar products with similar, cloned design. I know very well how a camera is designed as a piece of machinery, and I understand well how it operates; for me Canon - Nikon - Pentax - Olympus, etc, all just follow the same path and the same old concepts. Within the same price bracket I see no difference between the designs.

Sorry for this long-ish rant, and most likely unpopular view. As usually: yes, this is my personal view only, anyone is free to disagree. Yes, K20D is on my short list, but I still have faint hope that maybe we will see something really different in September... though I doubt it.

BTW, I found Camera Labs tests to be excellent and enjoyable to read, one more reason to be surprised that the hot pixels issue so many noticed was not even mentioned in the test.

I'm glad you found that document of interest. I tend to agree that most DSLRs are, to paraphrase, "good enough". That said, most of us find that how a camera feels "in hand" is surprisingly important and can be quite different not just between manufacturers but between different models in a particular manufacturer's range. So, as you get closer to making your choice please do get down to a store and take as much time as you need to handle the goods.

I'm glad you found that document of interest. I tend to agree that most DSLRs are, to paraphrase, "good enough". That said, most of us find that how a camera feels "in hand" is surprisingly important and can be quite different not just between manufacturers but between different models in a particular manufacturer's range. So, as you get closer to making your choice please do get down to a store and take as much time as you need to handle the goods.